Assume a specific IAM role with a container via docker-compose

docker_compose_assume_iam_role.sh

#!/bin/bash

# Assume the role using locally configured AWS credentials, then pass the assumed role to the container via environment 
# variables!

ASSUMED_ROLE=$(aws sts assume-role \
        --role-arn "arn:aws:iam::000000000000:role/our-role-to-assume" \
        --role-session-name "session_name" \
        --output text)


# 'docker-compose exec' seems to set the shell width incorrectly, here we overcome that by manually setting COLUMNS and
# LINES!
docker-compose exec \
        -e COLUMNS=$(tput cols) \
        -e LINES=$(tput lines) \
        -e AWS_ACCESS_KEY_ID=$(echo $ASSUMED_ROLE | awk '{print $5}') \
        -e AWS_SECRET_ACCESS_KEY=$(echo $ASSUMED_ROLE |  awk '{print $7}') \
        -e AWS_SESSION_TOKEN=$(echo $ASSUMED_ROLE |  awk '{print $8}') \
        container_name bash